When airways to a sublobar segment of lung are obstructed, collateral channels may provide ventilation (collateral ventilation) to that segment. The anatomic nature and extent of these channels may change with the maturational and aging process, and with development of pulmonary dysfunction. However, little is known of the physiologic evolution of these channels either during aging or with the development of lung dysfunction, and even less is known concerning the factors which influence them under these circumstances. Thus, the overall goal of this project is to examine collateral mechanics during development and lung dysfunction. The specific aims of this proposal are: 1) to characterize collateral mechanics at varying developmental stages, 2) to evaluate the role of collateral channels in the pathophysiology of lung dysfunction, and 3) to assess the role of a variety of factors known to regulate collateral channels at varying ages, and to determine the extent of this regulation in situations in which pulmonary function is abnormal. The regulatory factors to be examined are: mechanical (lung volume), respiratory gases (02 and C02), autonomic nervous system, and pharmacological agents. We will test the hypothesis that collateral channels increase with age and with the development of peripheral airway disease. In addition, we will test the hypothesis that factors known to regulate collateral channels change with age and peripheral airway disease. Studies will be performed in human patients and volunteers, and in anesthetized sheep of different ages. A peripheral bronchus will be obstructed with a fiberoptic bronchoscope and collateral resistance will be measured by infusing air at a constant flow through the bronchoscope and measuring the pressure in the obstructed segment. The time constant for collateral channels will be determined by stopping the flow of air and calculating the time for the pressure in the obstructed segment to fall 63%. The role that collateral channels play in the distribution of ventilation with age or development of lung dysfunction is unclear. The present experiments will elucidate the physiological function of collateral channels during the aging process and with lung dysfunction.